Scientists reported the first discovery of water in a planet outside of our Solar System:

The planet was discovered in 2005 as it dimmed the light of its parent star by some three percent when transiting in front of it. Using Spitzer, Tinetti and the team observed the star, which is slightly fainter than the Sun. They watched its starlight dim at two infrared bands (3.6 and 5.8 micrometres). [...]

“Water is the only molecule that can explain that behaviour,” says Tinetti.

The presence of water vapour does not necessarily make it a good candidate in the search for planets that harbour life. “This is a far from habitable world,” she adds.